Why does my cut-out cookie dough get dry and tough?

Tim asks: When I roll out sugar cookie dough for cut-out cookies, the dough becomes dry and tough.  Why is that?

BakingSOS says: You have probably worked too much flour into the dough when rolling it out.  Flour contains protein called gluten which gives strength and structure to baked goods.  But the more gluten in the dough, the tougher it becomes.  When rolling out sugar cookie dough, it’s important to dust your work surface with flour to keep the dough from sticking, but here are a few tricks to reduce the amount of flour you use, thus keeping your dough more tender and pliable:

•  I place my cookie dough between 2 pieces of waxed paper and dust the dough lightly with flour.  Then I roll out the dough with the rolling pin on top of the waxed paper.  This requires using less flour, which in turn, keeps your dough from drying out and becoming too tough.
• After you have cut out all the cookies from a batch of dough, gather the scraps into a ball, flatten it into a disk, wrap it in plastic wrap, and chill it in the refrigerator for at least 15 minutes to allow the dough to rest.  This will relax the gluten and make your dough more pliable.
• It is a good idea to only re-roll the scraps one time and then discard any leftovers.  Otherwise, you will eventually work too much flour into the dough, and it will become too tough to roll out.  (Though I have to admit that I usually re-roll my scraps more than once because I like to make as many cookies as possible!)